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    Subject[PATCH] tcp: do not promote SPLICE_F_NONBLOCK to socket O_NONBLOCK

    commit 11134aa8499b6fd67569e8fd21bde6fc481898d1
    Author: Octavian Purdila <>
    Date: Thu Jul 17 16:25:23 2008 +0300

    tcp: do not promote SPLICE_F_NONBLOCK to socket O_NONBLOCK

    This patch changes tcp_splice_read to the behavior implied by man 2

    SPLICE_F_NONBLOCK - Do not block on I/O. This makes the splice
    pipe operations non-blocking, but splice() may nevertheless block
    because the file descriptors that are spliced to/from may block
    (unless they have the O_NONBLOCK flag set).

    This approach also provides a simple solution to the splice
    transfer size problem. Say we have the following common sequence:

    splice(socket, pipe);
    splice(pipe, file);

    Unless we specify SPLICE_F_NONBLOCK, we can't use arbitrarily large
    transfer sizes with the 1st splice since otherwise we will deadlock
    due to pipe being full. But if we use SPLICE_F_NONBLOCK, the current
    implementation will make the underlying socket non-blocking and thus
    will force us use poll or other async I/O notification mechanism.

    Choosing a splice transfer size that won't deadlock is not trivial: we
    need to stay under PIPE_BUFFERS packets and since packets can have
    arbitrary sizes we will need to be conservative and use a small
    transfer size. That can degrade performance due to excessive system

    Signed-off-by: Octavian Purdila <>

    diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
    index 56a133c..cc5082b 100644
    --- a/net/ipv4/tcp.c
    +++ b/net/ipv4/tcp.c
    @@ -570,7 +570,7 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,


    - timeo = sock_rcvtimeo(sk, flags & SPLICE_F_NONBLOCK);
    + timeo = sock_rcvtimeo(sk, sock->file->f_flags & O_NONBLOCK);
    while (tss.len) {
    ret = __tcp_splice_read(sk, &tss);
    if (ret < 0)
    @@ -578,10 +578,6 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
    else if (!ret) {
    if (spliced)
    - if (flags & SPLICE_F_NONBLOCK) {
    - ret = -EAGAIN;
    - break;
    - }
    if (sock_flag(sk, SOCK_DONE))
    if (sk->sk_err) {
     \ /
      Last update: 2008-07-17 15:39    [W:0.020 / U:21.564 seconds]
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